ZYGOPHYLACIDAE QUELCH, 1885

Gu, Zhangjie, Ruthensteiner, Bernhard, Moura, Carlos J., Liu, Lihua, Zhang, Rui & Song, Xikun, 2022, Systematic affinities of Zygophylacidae (Cnidaria: Hydrozoa: Macrocolonia) with descriptions of 15 deep-sea species, Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) 196, pp. 52-87 : 60

FAMILY ZYGOPHYLACIDAE QUELCH, 1885

Diagnosis: Solitary hydrothecae arising from hydrorhiza directly, or erect, pinnate or flabellate colonies, with polysiphonic hydrocauli in most species, otherwise monosiphonic. Hydrocladia mostly arranged in one plane, alternate to subopposite. Hydrothecae mostly tubular, seldom campanulate or subuliform, with short to long pedicel, with one or two diaphragms, with or without indentation (intrathecal projections) at distal part of the hydrothecae, and with one to numerous nematothecae on hydrocauli, hydrocladia and/or apophyses of hydrocladia. Gonothecae congregate to form coppiniae on stem or its hydrocladia; coppiniae with or without defensive tubes, the latter occasionally provided with hydrothecae or nematothecae. Individual gonothecae solitary or adnate, generally elongate or ovoid, seldom flask- or carrot-shaped, apices either with a circular aperture or with one to three straight or curved short tubes.

Remarks: Molecular data contributed by the present study support the genetic distinction and validity of the family Zygophylacidae ( Figs 21 , 22 ). Based on specimens examined in this study and morphological diagnoses proposed by Rees & Vervoort (1987), Vervoort (1987) and Cornelius (1995), both zygophylacids and lafoeids have similar tubular hydrothecae. However, they differ in the fact that nematothecae and hydrothecal diaphragms are commonly present in Zygophylacidae , but are absent in Lafoeidae ( Bouillon et al. 2006; this study).

Figures

Figure 21. Maximum likelihood phylogenetic analyses with concatenated partial sequences of the 16S, 18S and 28S rRNA genes (5446 bp after multiple alignments) using the GTR+I+G model. Numbers near the nodes indicate bootstrap and Bayesian posterior probability values. Values lower than 50 or 0.5 were omitted and labelled with ‘<’. The scale bar represents 0.1 substitutions per site. Bayesian analyses using the GTR+I+G model. Sequences of species in bold were contributed by this study. ‘+’ (or ‘-’) indicates the families, or superfamily, use (or not) of opercular flaps or nematothecae as the protective strategies.

Figure 22. Phylogenetic analyses derived from partial sequences of the 16S rRNA gene (548 bp after multiple alignments). A, B, maximum likelihood analyses using the TIM2+I+G model; C, Bayesian analyses using the GTR+I+G model. A, with phylogram topology, the scale bar represents 0.2 substitutions per site; B, C, with transform cladogram topology. Numbers near the nodes indicate bootstrap or Bayesian posterior probability values, values lower than 50 or 0.5 were omitted; numbers alongside the taxa names indicate the last four digits of the GenBank accession numbers. Different topologies between different phylogenetic analyses in B and C are shown in colour. Sequences of taxa in bold are contributed by this study.